Laser scanning confocal microscopy has become a significant advance in optical microscopy, primarily because the technique enables visualization deep within living and fixed cells and tissues and affords the ability to collect sharply defined optical sections from which three-dimensional renderings of a specimen can be created. Confocal microscopy offers several advantages over conventional widefield optical microscopy, including control over depth of field, elimination or reduction of background information away from the focal plane, and the ability to collect serial optical sections from thick specimens. Confocal imaging typically relies on sequential collection of light from spatially filtered individual specimen points, followed by electronic-signal processing and ultimately, the visual display as corresponding image points. Typical confocal microscopes use a focused beam or line of excitation light to illuminate a point or line within the specimen. Scanning the focused excitation beam across the specimen focal plane can be accomplished by mechanically translating the microscope stage with respect to the fixed position of the focused excitation beam. However, mechanically translating the stage is a time consuming process. Alternatively, the excitation beam can be scanned across the focal plane by reflecting the beam off of a rotatable minor. However, rotating the minor creates a pivot axis that often results in a portion of the excitation beam being clipped by a plate located at the back of the objective, thereby reducing the irradiance of the excitation beam that reaches the focal plane.
Engineers and microscope designers have attempted to correct these problems by designing various lens-based systems to control the path of the excitation beam. However, lenses introduce unacceptable aberrations into the system for large scan angles as well as a substantially increased path length, and lenses also require additional alignment degrees of freedom which can add to system complexity. For the above described reasons, engineers, scientists, and microscope manufacturers continue to seek faster systems and methods for scanning confocal illumination of a focal plane.